Electric leakage is that a current flows out of an electric wire connected from a power source to a load. The electric leakage is actually detected according to the difference between the current flowing from the power source to the load and the current returning from the load to the power source. A conventional electric leakage detecting apparatus is proposed as an apparatus configured to detect the variations in the impedance of a ring-shaped magnetic material by passing two electric wires communicating a power source with a load through the hole of the magnetic material (Patent Literature 1).
An electric leakage detecting apparatus 100 is schematically illustrated in FIG. 24. The electric leakage detecting apparatus 100 includes a ring-shaped magnetic material 101, a magnetic impedance element 102 attached to the magnetic material 101, and a detector 103 configured to detect the variations in the impedance. A pair of electric wires 110 and 111 (referred to as an electric wire A and an electric wire B) extending from a power source 115 to a load 116 pass through a hole 104 of the ring-shaped magnetic material 101.
A magnetoresistive element of which resistance varies depending on the magnetic field is used as the magnetic impedance element 102. The magnetoresistive element is placed in the magnetic field that the ring-shaped magnetic material 101 generates. For example, a part of the ring-shaped magnetic material 101 is removed to form a gap, and then the magnetoresistive element can be placed in the gap. Needless to say, another manner is acceptable.
The detector 103 can be any material as long as the material can detect the variations in the resistance of the magnetoresistive element. The detector 103, for example, converts the variations in the resistance into a signal having a predetermined frequency, or reshapes a waveform using a filter circuit and an amplifier circuit, and then outputs the signal from a signal detection circuit to convert the signal into a main signal.
The operation of the electric leakage detecting apparatus 100 will be described. Without electric leakage, the current flowing in the electric wire A110 has the same amount as the current flowing in the electric wire B111 and the currents flow in the opposite directions. Thus, no magnetic flux arises in the ring-shaped magnetic material 101. Consequently, the resistance of the magnetic impedance element 102 does not vary at that time. On the other hand, with electric leakage, the current flowing in the electric wire A110 has a value different from the value of the current flowing in the electric wire B111. This generates magnetic flux in the ring-shaped magnetic material 101.
The generated magnetic flux varies the impedance of the magnetic impedance element 102. The detector 103 detects the generation of the electric leakage by detecting the variation.